Mobile communications systems are currently being developed to accommodate both the original FCC allocated spectrum, i.e. channels 1 to 666 for non-expanded spectrum (NES) use, and the additional FCC allocated spectrum, i.e. channels 667 to 799 and 991 to 1023 for expanded spectrum (ES) use. When a mobile subscriber wishes to make a call, a channel request is initiated so that a free channel can then be allocated to the mobile. In a practical system, particularly under busy conditions, a large number of channel requests will be made and these requests need to be queued to await processing. In current systems servicing both expanded spectrum (ES) and non-expanded spectrum (NES) mobiles, channel allocation is effected in the following way. The ES and NES mobiles making channel requests are placed in separate queues based on the time order in which the requests were made. For NES mobile requests only the NES channel queues are searched to find a free channel. For ES mobile requests however, both the ES and NES channel queues are searched, i.e. a NES channel is allocated only if all the ES channels are busy. This results in the ES channels being used at a much higher rate than the NES channels. During busy hours excessive interference can occur within the more heavily used expanded spectrum causing a consequent reduction in the perceived quality of service.